JPH06252543A - Method for soldering ic substrate - Google Patents

Abstract

PURPOSE:To provide a soldering method which does not cause a flat-package type IC to be thermally damaged even due to collective soldering with fused solder and any bridging between the pins of the IC. CONSTITUTION:When a heat insulating plate 3 is applied to a flat-package type IC 2 mounted to a printed circuit board 1 temporarily so that an overhang part 4 projecting from four sides of the IC 2 by 1mm is created and soldering is performed using a general automatic soldering device, it is dipped into a melted solder 5 after preheating and coating of flux and then the relative flow of the melted solder 5 is controlled by the overhang part 4 when the printed circuit board travels inside. Then, bridging between pins 6, 6... can be prevented. at the same time various kinds of soldering are performed, and then the damaging of the IC2 due to the melted solder 5 can be prevented owing to the heat insulating plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for soldering an IC substrate in which a substrate on which required components are temporarily attached is dipped in a molten solder bath for soldering, and particularly, a substrate on which an IC of a flat package type is temporarily attached is used. The present invention relates to a soldering method for an IC substrate, which ensures soldering without destruction due to heat or a bridge between pins.

[0002]

2. Description of the Related Art When assembling a board of an electronic device,
The main component is the flat package type I
Regarding C, a method of temporarily attaching this to a substrate in advance and then immersing it in molten solder to perform soldering is the high heat at that time (250
Since there is a high possibility that the circuit formed on the IC chip will be destroyed by (.degree. C.), it is hardly adopted. Further, in such a method, there is a serious problem that a bridge between IC pins is likely to occur.

Therefore, one general technique is to temporarily attach only the parts excluding the flat package type IC, which is weak against heat stress, to the substrate, and then immerse the substrate in the molten solder automatically or manually to perform the collective soldering. After this, there is a method in which an operator manually solders the flat package type ICs one by one. But according to this method,
Since it is a two-step process and the latter half of the process is time-consuming manual work, it is extremely inefficient as a whole. In addition, in the latter half of the manual IC soldering process, the distance between pins is extremely small. Even a highly skilled worker has a problem that it is difficult to perform accurate soldering and a defect is likely to occur.

As another technique, a flat package type IC is soldered by a reflow method using a chip mounter (automatic component mounting machine), and other components are thereafter soldered to a substrate by a general technique. There is a method in which the solder is temporarily attached and then immersed in molten solder for soldering. However, this method has a drawback that the number of steps is increased by one and the cost is increased.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems as described above, and enables flat package type ICs, which are susceptible to thermal stress, to be collectively soldered together by melting solder together with other components. In addition to the above, it is an object of the invention to provide a method for soldering an IC substrate in which a bridge between pins of an IC does not occur during soldering.

[0006]

SUMMARY OF THE INVENTION The gist of the present invention is to perform soldering by immersing a soldering surface of a substrate on which required components including a flat package type IC are temporarily attached in a solder bath. In the method of soldering the IC substrate, on the upper surface of the package of the flat package type IC,
This is a soldering method for an IC substrate, in which a heat insulating plate is joined in a state of overhanging from all sides thereof and then the soldering surface of the substrate is immersed in a solder bath.

The heat insulating plate is not only a plate-like member, but also a pin protecting member that protrudes to the lower part of the shoulder of the IC pin at a portion that will overhang when it comes into contact with the upper surface of the IC package. It is also possible to employ a structure in which a portion is formed and a protection groove into which the shoulder of the pin can be inserted is formed in the pin protection portion. In the latter case, the heat insulating plate is brought into contact with the upper surface of the IC package while inserting the shoulder portion of the pin into the protection groove.

The overhanging width of the overhanging portion of the heat insulating plate or the protruding length of the pin protecting portion protruding to the overhanging portion depends on the solder adhesion state in the soldering process when it is immersed in the molten solder, and the like. Appropriately decided in consideration of the coating situation in the preceding flux coating process.

That is, when the substrate moves in the solder bath, the relative flow of the molten solder is appropriately controlled by the overhang portion or the pin protection portion of the heat insulating plate, and as a result, the IC
In order to ensure that a proper amount of solder adheres to the required soldering parts of the pins, a reliable connection is obtained, and at the same time a bridge between the pins is prevented, the overhang width of the overhang portion or the pin protection portion Properly determine the protruding length of. Further, at the same time, also in the flux tank, the relative flow of the flux is appropriately regulated, and the overhang portion is overhanged so that the amount of the flux applied to the portion to be applied of the IC pin is appropriate. The width or the protruding length of the pin protection portion is appropriately determined.

The overhanging width of the overhang portion or the protruding length of the pin protection portion should be properly determined by observing the condition sufficiently. Therefore, the heat insulating plate is responsible for the heat insulating action on the flat package type IC when the solder is immersed in the molten solder, and also ensures the reliable soldering of the required soldering portions of the pins, and at the same time, bridges between the pins. It is in charge of the action of preventing. As the material of the heat insulating plate, phenol resin or any other material having appropriate heat insulating properties and heat resistance capable of withstanding the temperature of the molten solder can be freely selected. Regarding the internal structure, for example, a hollow structure having an improved heat insulating property can be freely adopted. From the viewpoint of heat insulation, it is also possible to apply a paste-like solder mask instead of these heat insulation plates.

[0011]

Since the present invention is configured as described above, a flat package type IC that is temporarily attached to a substrate in which a component is temporarily attached is automatically or manually dipped into a molten solder bath for soldering. With regard to the above, a heat insulating plate is joined to the upper surface of the package, and then flux is applied to a required portion by a general technique, and subsequently, as described above, soldering is performed by immersing in the molten solder in the solder bath. . The heat insulating plates are joined on the four sides so as to slightly overhang from the upper surface of the package. The width of the overhang differs depending on the size of the IC package, but in most cases around 1 mm is appropriate. When the heat insulating plate having the pin protection portion is used, the shoulder portion of the pin is inserted into the protection groove at the time of joining to the upper surface of the package.

When the flux is applied and the soldering is performed in this manner, it goes without saying that the components other than the flat package type IC can be processed in the same manner as the general technique, and the flat package type IC can be processed. The heat insulation effect of the heat insulation plate prevents damage from the heat from the molten solder, and the flux is properly applied to the soldering part of the pin. In addition, the overhang part of the heat insulation plate or the pin protection part Allows the relative flow of molten solder to be properly controlled, so that the pins are soldered reliably and without bridging.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be disclosed below with reference to the drawings showing embodiments. A first embodiment will be described with reference to FIGS. Required components including a flat package type IC 2 are temporarily attached to the substrate 1 in advance by a general technique. After that, as shown in FIGS. 2 and 3, a square heat insulating plate 3 when viewed from above is attached to the upper surface of the IC package. In this example, the soldering paste was used. Other than this, it is also possible to attach it using a commercially available double-sided tape or the like.

The heat insulating plate 3 is formed by cutting a phenol resin plate into a dimension in which each side is longer by 2 mm than the plane dimension of the IC 2, and the attachment is performed as shown in FIGS. 1 and 3. , So that the four sides form the overhanging portions 4 protruding by 1 mm from the four sides of the IC2.

After preparing in this way, soldering is performed by a general technique of immersing in the molten solder 5 in the solder bath. In this example, a general automatic soldering device was used. Although not shown, this automatic soldering apparatus is, as is well known, a solder bath and a preheating portion installed in the preceding stage thereof, a flux bath for applying flux to a soldering required portion of the substrate 1, and a preheating portion side. To the rear of the solder bath.

However, when soldering is performed using such a general automatic soldering apparatus, the target substrate 1 is carried by the transport mechanism, preheating in the preheating section and application of flux in the flux tank are performed. And then transferred to the solder bath,
The surface of the substrate 1 on which the soldering-required portion is present is immersed in the molten solder 5. In this way, the components other than the flat package type IC2 are soldered in the same manner as the general technique, and the flat package type IC is used.
As for 2, the molten solder 5 is heated by the heat insulating plate 3.
The damage due to heat from the pins 6 is prevented, and the pins 6, 6 ... Are soldered securely. After the soldering is completed, the heat insulating plate 3 is removed.

That is, the flat package type I
Due to the action of the heat insulating plate 3 attached to the upper surface of the C2 package, the heat of the molten solder 5 is first blocked, and the IC 2 is protected from its high heat (about 250 ° C.). Further, since the overhanging portions 4 projecting from the package of the IC 2 are formed on the four sides of the heat insulating plate 3, the relative flow of the molten solder 5 is appropriately controlled when the substrate 1 moves in the solder bath. Since the breakage is good, the bridge between the adjacent pins 6 and 6 is prevented, and on the other hand, necessary solder is attached and reliable soldering is performed. Regarding the application of the flux in the flux tank, the presence of the overhang portion 4 to the above extent does not hinder the application.

4 to 6 show a second embodiment of the present invention. Required components including a flat package type IC 12 are temporarily attached to the substrate 11 in advance by a general technique. Thereafter, as shown in FIGS. 5 and 6, the heat insulating plate 13 having a square shape when viewed from the top and having the pin protection portion 17 protruding around the bonding surface to the upper surface of the package is mounted on the IC 12 described above.
Stick it on the top of the package. The pin protection portion 17 is formed with protection grooves 18, 18 ... In which the shoulders of the pins 16, 16 of the IC 12 can be inserted.
The shoulders of the pins 16, 16 ...
Try to fit in each. The heat insulating plate 13 was attached using a double-sided adhesive tape in this example. The adhesive or the like as the attaching means can be freely adopted as long as it can hold the heat insulating plate 13 on the upper surface of the package during the soldering work. The heat insulating plate 13 is made of phenol resin.

After the preparation as described above, the soldering work is carried out in the same procedure as in the first embodiment. Also, the obtained effects are almost the same.

[0020]

According to the method of soldering an IC substrate of the present invention, a heat insulating plate is joined to the upper surface of a flat package type IC package for soldering. First, the heat of the molten solder is cut off,
C will be protected from its high heat (about 250 ° C).

Further, since the overhang portion or the pin protection portion protruding from the IC package is formed on the four sides of the heat insulating plate, the relative flow of the molten solder is appropriately controlled when the substrate moves in the solder bath. As a result, solder breakage becomes good, bridges between adjacent pins are prevented, and necessary solder adheres to the other surface to ensure reliable soldering. Regarding the application of the flux in the flux tank, the overhang or the protrusion of the pin protection portion as described above does not hinder the application.

[Brief description of drawings]

FIG. 1 is a partially cutaway side view of a first embodiment showing a state of a board moving in molten solder.

FIG. 2 is a partially cutaway side view of the first embodiment showing a state where a heat insulating plate is bonded and attached to a flat package type IC package.

FIG. 3 is an explanatory plan view of the first embodiment showing a state in which a heat insulating plate is bonded and adhered to a flat package type IC package.

FIG. 4 is a partially cutaway side view of the second embodiment showing a state of a substrate moving in molten solder.

FIG. 5 is a partially cutaway side view of the second embodiment showing a state in which a heat insulating plate is bonded and attached to a flat package type IC package.

FIG. 6 is an explanatory plan view of a second embodiment showing a state in which a heat insulating plate is bonded and attached to a flat package type IC package.

[Explanation of symbols]

 1 substrate 2 IC 3 heat insulating plate 4 overhang part 5 molten solder 6 pins 11 substrate 12 IC 13 heat insulating plate 16 pins 17 pin protection part 18 protection groove

Claims (2)

[Claims] 1. A method of soldering an IC substrate, wherein a soldering surface of a substrate, to which required components including a flat package type IC are temporarily attached, is dipped in a solder bath for soldering. The method for soldering an IC substrate, wherein a heat insulating plate is joined to the upper surface of the package in a state of overhanging from all sides of the package, and the soldering surface of the substrate is immersed in a solder bath. 2. A pin protection portion projecting to a lower portion of a shoulder portion of the IC pin at a portion of the heat insulating plate that is overhung when the heat insulating plate is joined to the upper surface of the IC package. And a protective groove in which the shoulder portion of the pin can be inserted is formed in the pin protection portion, and the heat insulating plate is joined to the upper surface of the package of the IC while inserting the shoulder portion of the pin in the protection groove. The method for soldering an IC substrate according to claim 1,